1. Field of the Invention
The invention relates to carbon nanocapsules, and in particular to functionalized carbon nanocapsules.
2. Description of the Related Art
A carbon nanocapsule is a polyhedral carbon cluster constituted by multiple graphite layers having a balls-within-a ball structure. The diameter of a carbon nanocapsule is about 3-100 nm. There are two types of carbon nanocapsules: hollow and metal-filled. The center of a hollow carbon nanocapsule is, of course, hollow, while that of a metal-filled nanocapsule is filled with metals, metal oxides, metal carbides, or alloys.
Carbon nanocapsules were first discovered with carbon nanotubes in 1991, in the process of producing carbon nanotubes. Owing to the strong van der Waals force between carbon nanocapsules and carbon nanotubes, it is not easy to isolate carbon nanocapsules from the carbon nanotubes. In addition, the amount of carbon nanocapsules produced with carbon nanotubes is only enough for structural observation under electron microscope, thus the application thereof is obstructed.
By continuous research, processes producing high-purity hollow carbon nanocapsules as well as magnetic metal-filled carbon nanocapsules have been developed. (Please refer to U.S. patent application Ser. Nos. 10/255,669 and 10/329,333) With their special fullerene structure and optoelectronic properties, carbon nanocapsules can be utilized in various fields such as medicine (medical grade active carbon), light and heat absorption, electromagnetic shielding, organic light emitting materials, solar energy receivers, catalysts, sensors, carbon electrodes in lithium batteries, nanoscale composite materials with thermal conductivity and special electrical properties, and nanoscale carbon powder for printing. However, owing to the non-solubility of carbon nanocapsules, the related application is limited and insufficient.